Large scale buildings in cold districts may need cooling even in the condition the atmosphere is cold in winter, particularly in a data center, etc. where a large amount of heat is generated by communication service equipment. Therefore, generally, room coolers are operated there even in winter.
The air conditioning system generally used for air conditioning of a building is composed of, as shown in FIG. 2, an outdoor heat exchanger 102 functioning as a condenser, a receiver 108, an indoor heat exchanger 101 functioning as an evaporator, a compressor 110, and an expansion valve 104. The system performs a vapor compression refrigerating cycle which is an energy consuming refrigerating cycle.
However, in a cold district where the atmospheric temperature is low in winter, a natural refrigerant-circulation system is used as an energy-saving air conditioning system.
Said natural refrigerant-circulation system utilizes the phase-change of the refrigerant to effect natural circulation of the refrigerant based on the thermo-siphon principle caused by the effect of temperature difference of the refrigerant. By the system, energy saving and reduction of running cost are achieved.
Among a variety of natural refrigerant-circulation system proposed in the past, a system proposed recently will be explained hereunder with reference to drawings.
Said proposal is disclosed in Japanese Laid-Open Patent Application No.10-300128 as “Natural refrigerant-circulation chilling and dehumidifying apparatus and air-conditioning system combined with the apparatus”. The proposal relates to air-conditioning or dehumidification or indirect air conditioning utilizing outside cold air of a house or office building, and was made to solve the problems that a conventional air-conditioning apparatus which works on a vapor compression refrigerating cycle consumes a large amount of energy and enhances environmental pollution. There are disclosed a first, second, and third embodiment in the proposal.
The first embodiment of said proposal is, as shown in FIG. 3, composed of an indoor heat exchanger 101, an outdoor heat exchanger 102, and a refrigerant piping 103. The indoor heat exchanger 101 is provided in a room for exchanging heat with the air in the room. The outdoor heat exchanger 102 is provided in the outside of the separating wall A for changing heat with the outside air and located at the position higher than that of the indoor heat exchanger 101. The refrigerant piping 103 connects the indoor heat exchanger and outdoor heat exchanger so that the low boiling point refrigerant (HCFC-22, HFC-23) in the system circulates through the indoor heat exchanger 101 and outdoor heat exchanger 102.
With the configuration, the low boiling point refrigerant enclosed in the refrigerant piping is heated in the indoor heat exchanger 101 by the heat of the air in the room to be boiled and evaporated. The evaporated low boiling point refrigerant gas flows upward in the refrigerant pipe 103 and cools and dehumidifies the air passing through the indoor heat exchanger 101.
The low boiling point refrigerant gas flew upward in said refrigerant piping is introduced into the outdoor heat exchanger 102 and thereby cooled by the outside air to be condensed to a liquid state. The liquefied low boiling point refrigerant flows downward in the refrigerant piping by the effect of gravity to be again returned to the indoor heat exchanger 101 to be evaporated. Thus the evaporation condensing cycle is reiterated.
When outside air temperature is lower than the air temperature in the room, the pressure in the evaporator is higher than that in the condenser, so that refrigerant-circulation occurs without enforcing power. Thus, the heat in the room can be transferred to the outside of the room without enforcing power, and the air in the room can be dehumidified. As a result, substantial energy-saving can be attained. That is, the characteristic of the proposed natural refrigerant-circulation chilling and dehumidifying apparatus is determined by the difference in specific gravity of the low boiling point refrigerant caused by the phase-change thereof, difference in height of the liquid column of the low boiling point refrigerant, refrigerant piping system, the characteristics of the indoor heat exchanger and outdoor heat exchanger.
Next, the second embodiment of the proposal will be explained with reference to FIG. 4.
As shown in FIG. 4, the second embodiment of the natural circulation chilling and dehumidifying apparatus comprises an indoor heat exchanger 101, an outdoor heat exchanger 102, a refrigerant piping 103, an expansion valve 104, and a separate forced refrigerant-circulation refrigerating apparatus (a vapor compression refrigerating apparatus).
The vapor compression refrigerating apparatus 105 comprises an evaporation heat exchanger 150, a condensing heat exchanger 151, a compressor 152, and an expansion valve 153. The evaporation heat exchanger 150 of the vapor compression refrigerating apparatus 105 is in close contact with the outdoor heat exchanger 102 in order to efficiently take away heat from the outdoor heat exchanger 102. Reference symbol A denotes a wall, the left side thereof being a room and the right side thereof being the outside.
With the above configuration, said vapor compression refrigerating apparatus 105 is operated only when the temperature difference between the inside and outside of the room becomes small and cooling ability is reduced, in order to backup the heat exchanging ability of the outdoor heat exchanger 102.
Next, the third embodiment of the proposal will be explained with reference to FIG. 5.
As shown in FIG. 5, the third embodiment of the natural refrigerant-circulation chilling and dehumidifying apparatus consists of a vapor compression refrigerating/heat pumping apparatus 106 of prior art and the natural refrigerant-circulation chilling and dehumidifying apparatus 107 shown in FIG. 3.
Said vapor compression refrigerating and heat pump apparatus 106 works on a conventional energy-consuming vapor compression refrigerating cycle and comprises an indoor heat exchanger 160, an outdoor heat exchanger 161, a compressor 162, an expansion valve 163, and a refrigerant piping 164 connecting them in a loop. Reference symbol A denotes a wall, the left side thereof being a room and the right side thereof being the outside.
The compressor 162 is for compressing the low boiling point refrigerant filled in the system. The refrigerating cycle and heat pump cycle can be switched to each other according to whether the compressed refrigerant gas is introduced to the outdoor heat exchanger 161 or to the indoor heat exchanger 160.
In above configuration, the vapor compression refrigerating/heat pumping apparatus 106 is an air conditioning apparatus provided besides the natural refrigerant-circulation chilling and dehumidifying apparatus 107. When the natural circulation of the refrigerant occurs sufficiently, energy-saving operation with the vapor compression refrigerating cycle operation stopped can be performed, or the heat pumping cycle operation of the vapor compression cycle to warm the room can be performed while dehumidifying by the operation of the natural refrigerant-circulation cycle. The two systems work independently.
When considering the case the proposal disclosed in Japanese Laid-Open Patent Application No.10-300128 is used in a cold district, the second and third embodiments can accommodate enough to the environment, however, two sets of indoor heat exchangers, outdoor heat exchangers, and refrigerant pipe lines are necessary to be provided, and there is a problem of the high cost of equipment.
Further, one of the two systems is the equipment for backing-up when outside temperature is high, so the utilization factor of the equipment is low and accordingly the investment efficiency is low.